The primary purpose of this proposal is to develop event related potential measures and associated techniques for assessing neuro-behavioral functions in learning disabled (LD) and normal children and for differentiating among subgroups of LD children. A second aim is to cross-validate these measures in a sample of children who are genetically at risk for a learning disability, and to study the familial similarity of the measurements in affected parents and children. The brain mechanisms and functions measured will be those associated with the active selection and interpretation of different types of stimulus information (physical vs semantic) due to task relevance and/or previous experience, rather than with the passive coding of stimulus parameters per se. The ERP methodology employed is somewhat unique in that the ERP waveform will be considered as a complex measure of the serial and parallel time-course of neural information processing in many areas of the brain. Specific processes will be isolated by the carefully manipulation of behavioral task requirements and analysis of the resulting changes in the time-course and scalp distribution of the entire ERP waveform. Peak-to-trough and multivariate measures also will be used to quantify changes in ERPs. The results are of potential significance in that they should provide objective, electrophysiological methods for differentiating between normal and LD children and between different types of LD children. They also should provide information about the nature of brain mechanisms involved in different types of anomalous processing and the genetic vs environmental influences on these mechanisms. Such information would be invaluable in selecting appropriate treatment for different types of LD children.